Creating functions and reuse in other test scripts

I have searched for the solution and found multiple answers but didn’t work for me.

Under Collection Folder/Parent folder → Under Pre-request script …
[Note - env_amount is created under Collection Folder → Variables tab]

function getAmount()
{ const amount= (“random_number”, _.random(1, 10));

In the later folders/ tests - need to get this amount in ‘Body’ request. So I have added the following stmt to Pre-request of that test:
var amount=pm.collectionVariables.get(“getAmount”)();

In the body of the test -
“amount”: {{amount}},

its not working.

Your function is trying to set an environment variable, where in the pre-request script you have it trying to retrieve a collection variable that doesn’t appear to be declared anywhere.

The best way to declare a function is to define it as a global variable (don’t use LET, VAR or CONST)

utils = {
    getAmount: function (pm) {
        const amount = ("random_number", _.random(1, 10));
        pm.environment.set("env_amount", amount);
        return 'hello';
    response: function (pm) {
        return 'hello';

If you need access to Postman functions like pm.response or pm.environment, then you have to pass pm as an argument to the function.

Calling the function is then straight forward.

utils.getAmount(pm); //or

All you should need for your body is the following.

    "amount": {{env_amount}}

This will use the environment variable you set in the function.